The present invention relates to an eyeglass-frame, and more particularly relates to an improved construction of bows for an metallic eyeglass-frame.
An eyeglass-frame with excellent fitness to the wearer's facial construction and high workability is increasingly damanded not only in the medical fields for use as an eyesight improver but also in the field of fashionable world.
An eyeglass-frame in general comprises a pair of rims each holding a lense and a pair of bows or sided for stably holding the rims in position on the wearer's facial construction. In particular the bows are regarded as the most important elements in the construction of the eyglass-frame. It is intensely required for the bows to be able to hold the eyeglasses on the wearer's facial construction for an appreciable long period without causing any uncomfortableness and fatigue on the wearer. To this end, lots of proposals have been made regarding improvement of an eyeglass-frame from the viewpoint of both construction and material.
In the construction of a typical conventional eyeglass-frame, each bow includes a core made up of stainless steel, copper alloy, or nickel base alloy including chromium or copper, and a gold covering or sheath clad to the core. These metallic materials, however, have an inbred disadvantage to develop so-called plastic deformation when an external force beyond a certain limit is applied to the bows, in particular when such a large force is applied repeatedly. As a consequence, when the bows are too much pulled sideways during use of the eyeglasses, such a plastic deformation tends to be developed on the bows whilst leaving a permanent strain and disenables correct and stable positioning of the eyeglasses on the wearer's facial construction. In addition, seasonal change in temperature of the environment is liable to wield a great influence upon the mode of fitness of the bows to the wearer's face in particular in facial sections such as the temples an ear lobes, thereby furthering uncomfortableness and fatigue on the wearer of the eyeglasses.
In order to avoid the above-described disadvantages, it is thinkable to use, as the material for the bows of an eyeglass-frame, a metallic material having a high elastic limit or a super elastic material such as nickel-titanium alloys. Use of such a super elastic material, in particular use of nickel-titanium alloys tends to disenable smooth blazing of parts forming the eyeglass-frame, drawing or pressing for a shaping of the bows, and plating for decoration and/or anti-erosion purposes.
It is the object of the present invention to provide an improved metallic eyeglass-frame with significantly high elastic limit which assures long-lasting stability and ideal fitness in use with excellent workability in production.
In accordance with the basic aspect of the present invention, at lease each bow of an eyeglass-frame is provided with a core-to-covering clad structure in which a core is made of an alloy chosen from a group consisting of copper-tin zinc alloys, copper-aluminum-zinc alloys and copper-aluminum-nickel alloys, and a covering clad to the core is made of silver, silver base alloys, gold or gold base alloys.